Zinc plays an important role in activity expression and structural maintenance of many enzymes such as carbonate dehydrogenase, carboxypeptidase and alkaline phosphatase, and it is a trace element essential for the function and homeostasis of the living body.
Since zinc is not synthesized in the living body and zinc in the living body is lost in urine, feces or sweat, its intake from daily diet is very important. It is known that a decrease in the intake of zinc causes zinc-deficient conditions such as dysgeusia, poor appetite, delay in remedy of wounds, ateliosis, skin diseases, gangrene of hands and feet, change in nails, loss of hair and reduction in immune ability.
However, zinc salts such as zinc gluconate and zinc sulfate can be used only in substitute foods for mother's milk. To add zinc to liquid formula, foods for medical purposes and other processed foods, there is no means except for use of food and drink containing zinc at high levels. It is known to use oyster meat as a source of supply of zinc derived from food and drink (Japanese Published Examined Application No. 63672/92 and Japanese Published Unexamined Application No. 19385/96), but the use of oyster meat is limited and its processability in food manufacturing is low because of its peculiar smell and the fact that nourishing components in oyster vary depending on four seasons. It is also known to use extracts from seaweed powder, livers of poultry, animals, etc., wheat bran and rice bran (Japanese Published Unexamined Patent Application No. 88964/92), but due to their flavors, there is a limit to foods to which they can be applied.
On the other hand, there is known a process for producing whey calcium which comprises neutralizing a whey mineral solution to pH 6.0 to 8.0 and recovering the resulting insolubles (Handbook of Materials for Food Development, Korin, pp. 553-558, Japanese Published Examined Patent Application No. 60303/90). However, said whey calcium contains only about 0.002 to 0.45 g/kg zinc.
Accordingly, there is demand for a source of supply of zinc being good in flavors, having high processability in food manufacturing and containing zinc at high levels.
The content of calcium in said whey calcium is 400 to 500 times or more than the content of zinc, but the amounts of calcium and zinc required for an adult per day are about 600 mg and about 8 mg respectively, so there is demand for whey minerals whose calcium content is not more than 75-fold relative to the zinc content.